Meta-searching library communities involve access to sources where metadata are invisible behind query interfaces. Many of the query interfaces utilize predefined abstract Access Points for the implementation of the search services, without any further access to the underlining meta-data and query methods. The existence of unsupported Access Points and its consequences, which are either query failures or inconsistent query answers, creates a major issue when meta-searching this kind of systems. An example of the abstract Access Point based search model is the Z39.50 information retrieval protocol, which is widely used by the library community. In this paper we present the zSAPN (Z39.50 Semantic Access Point Network), a system which improves the search consistency and eliminates the query failures by exploiting the semantic information of the Access Points from an RDFS description. The current implementation of zSAPN is in the context of the Z39.50 protocol, using the official specification of the Access Point semantics and can benefit the huge number of the available sources worldwide. zSAPN substitutes each unsupported Access Point with a set of other supported ones, whose appropriate combination would either broaden or narrow the initial semantics, according to the user's choice. Finally, we estimate the impact of the modification of the initial semantics during the substitution process to the precision or the recall of the original query, with the unsupported Access Point. © 2008 Springer-Verlag Berlin Heidelberg.